Recently, a concept of Service Path Routing (SPR) has been introduced in internet protocol (IP) nodes. According to SPR, packets traversing an IP node are routed through a pre-defined set of hardware cards, also called blades. Each packet entering the IP node is classified and assigned to a service path defining which blades of the IP node are to be visited by the packet and treated thereat.
Solutions based on SPR propose a special forwarding engine (FE) to classify packets and add a special indication to a packet, to determine a service to which this packet belongs. The FE needs to be invoked after each service blade has performed its task in order to determine if another service blade needs to further process the packet. Hence, the FE is generally present on each service blade, or shared by several service blades.
Current solutions require FEs at multiple components (e.g. several cards or blades) of an IP node. Because FEs are complex and expensive, this requirement has so far prevented a wide adoption of the SPR concept. In addition, while an instance of the FE may in principle be shared by multiple blades, presence of an FE instance on every service blade is required for maximum performance. This latter requirement may only come at the expense of increased costs of the service blades.